Starting series of compressors



Feb. 7, 1950 D. E. MEITZLER 2,496,305

STARTING SERIES OF COMPRESSORS Filed Jan. 30, 1945 1 5 Sheets-Sheet 1FIG.|.

INVENTOR x/ma zim/ Feb. 7, 1950 D. E. MEITZLER STARTING SERIES OFCOMPRESSORS 5 Sheets-Sheet 2 Filed Jan. 30, 1945 N ON INVENTOR Feb. 7,1950 D. E. MEITZLER 2,495,805

STARTING SERIES OF COMPRESSORS Filed Jan. 30, 1945 5 Sheets-Sheet 3 I27TO EXHAUST w:- v -Iy' mi/1101112 MANIFOLD I 1", I 1W1 INVENTOR Feb. 7,1950 D. E. MEITZLER 2,496,805

STARTING SERIES 0F COMPRESSORS Filed Jan. 30, 1945 5 Sheets-Sheet 4BALANCE PUMP Feb. 7, 1950 D. E. MEITZLER 2,496,805

STARTING SERIES OF COMPRESSORS Filed Jan. 30, 1945 5 Sheets-Sheet 5 TOGAS SUPPLY g INVENTOR MMZ W Patented at. 7, 1950 2,498,805 s'raa'rmcscams or comrarzssons Donald E. Meitzler, Manchester, Conn., assignor toUnited Aircraft Corporation, East Hartford, Conn., a corporation ofDelaware Application January 30, 1945, Serial No. 575,341

2 Claims. (Cl. 230-56) 1 v This invention relates to a starting systemfor power plants including a number of free-piston units.

In a power plant of this type the controls may be located at a pointremote from the units. A

feature of this invention is an arrangement by 1 which the starting ofany one of the units may be controlled from a control station. Anotherfeature is a single control by which any one of the units may be startedselectively.

If the power plant is used in aircraft, the weight of the power plantshould be kept at a minimum. A feature of this invention is anelectrical control for the starting systems of the units which willpermit the elimination of separate hydraulic or pneumatic lines fromeach of the units to the control station.

A feature of this invention is a selector by which the operator maydetermine which unit is to be started, the selector being so arrangedthat the starting system for each unit may continue to functionautomatically until the unit is runnine.

The copending application of Meitzler, Serial No.. 550,894 Patent No.2,469,739 of May 10, 1949), described a starting system in which thefree-piston unit may be started automatically by admitting fluid underpressure to the starting system. In some installations, it may beundesirable to have the starting systems for all of the units operatingsimultaneously. A feature of this invention is a control by which theseveral units may be started successively and by which anyunit may bestarted if it stalls.

Other objects and advantages will be apparent from the specification andclaims, and from the accompanying drawings which illustrate anembodiment of the invention.'

Fig. l is a side elevation of the power plant.

Fig. 2 is a sectional view through the compressor with the startingdevice in elevation.

Fig. 3 is a sectional view of the starting device and the release valve.

' Fig. 4 is a sectional view of the cranking device and the supplyvalve.

Fig. 5 is a diagrammatic view of the starting system for the units.

The'power plant may include a number of freepiston units 2 acting as gasgenerators and delivering gas to an exhaust collector. 4. The: exhaustcollector may be surrounded by a'scavenge collector l for the compressedgasfrom the unit which'is used in scavenging the engine cylinder. Aburner 11 which may be located within the exhaust collector is connectedto-a turbine {which I entire drives a propeller system, not shown, on ashaft 9. The units arearranged in groups around the gas collector andoperate independently of one another.

The unit shown includes an engine cylinder l0 having reciprocatingpistons i2 and H to which compressor pistons l6 and it in cylinders 20and 22 are integrally connected. Sleeves 24 and 26 attached to thecompressor pistons complete the reciprocating piston assemblies. Thesleeves reciprocate over stationary pistons 28 and 30 and form airspring cylinders.

The piston assemblies are moved apart by the burning of fuel injectedinto engine cylinder Ill through one or more nozzles 32. Air compressedin the air spring cylinders on the power strokereturns the pistonassemblies. The assemblies are always maintained at equal distances fromthe center of the engine cylinder by a linkage, which may include racks34 and, Fig. 4, projecting from the piston assemblies and meshing with apinion It on a shaft 40.

'Intake manifold 42 conducts air to intake valves M in the heads of thecompressor cylinders through which air alternately enters opposite endsof the compressor cylinders. The compressed air leaves the cylindersthrough discharge valves 48, also at opposite ends of the compressorcylinders and passes into a central scavenge chamber 48 and end chambers50 and 52. These chambers may be interconnected by a scavenge manifold,not shown. Compressed gas from the chambers enters engine ports 54 and5B which are uncovered by pistons l2 and It at the end of the powerstroke, thereby permitting air to be blown through the engine cylinder.Gas and air in the engine cylinders is discharged through exhaust portsSI into exhaust manifold 60.

Starting-devices 62 for the unit are mounted in the air spring pistons28 and 30. The devices are similar and only one device will be describedin detail. Piston forms a housing having an accumulator chamber 63 inwhich gas under pressure is collected in readiness for starting. Thischamber communicates with the air spring cylinder through a port 54closed by a poppet valve 88. The stem it of this valve is slidable in ahold the valve closed during operation of the unit.

Cap 12 has a bore forming a cylinder 14 which receives a piston 16 onthe end of valve stem 88. The inner end of cylinder 14 is connected withthe storage chamber by one or more ports 18. A coil spring 80 in thecylinder moves the piston toward valve closing position. A head 82closes the outer end of cylinder 14 and is held in position by studs 84extending through both head 82 and-cap 12.

A casing 86 on head 82 has a bore 88 in which a plunger 90 is slidable.One end of bore 88 is closed by head 82, the other end by a cover plate82. Gas under pressure is admitted to the inner end of bore 88 through achannel 84 in casing 86. With plunger 80 in the position shown. gasentering the inner end of the bore 88 through channel 84 is guided intochamber 68 through a small passage 86 extending between bore 88 and apassage 88 in casing 86, cap 82, and head I2, and the head of piston 80.

Passage 88 intersects bore 88 in alignment another passage 98 whichcommunicates with the outer end of cylinder 14. Plunger 80 is normallyin a position to cut off fluid connection between passages 98 and 89,and has a groove I00, which. when the plunger is moved to the oppositeend of its stroke, connects these passages and permits gas to flowthrough channel 88 into the outer end of cylinder 14, to cause valve 66to open. I

For moving plunger 80 to the inner end of its stroke, casing 86 has agas inlet passage I02 which is connected by a groove I08 in plate 82 tothe outer end of bore 88. When gas under pressure enters this inletpassage, it moves plunger 80 to the left into a position to cover theend of passage 86 and to connect passages 88 and 99 by means ofgroove Ito establish fluid connection between chamber 68 and the outer end ofcylinder 14. When this occurs, the pressures on opposite sides of piston16 are balanced and the pressure on valve 66 opens the valve for theescape of gas into the air spring.

In starting the unit, gas under pressure is first admitted throughchannel 94 until a predetermined pressure is built up in chamber 68.After this pressure is reached, gas under pressure is admitted throughpassage I02 thereby moving plunger 90 to close passage 86 and to causevalve 66 to open. Before this action occurs, the piston assemblies ofthe unit will have been moved to starting position. The sudden inrush ofair into the air springs vfrom chambers 63 in starting devices 56 and 58will move the piston assemblies rapidly toward each other.

The starting devices 62 may be controlled by an automatically operatingrelease valve I04 which controls the admission of gas under pressure tochannel 84 and passage I02. Valve I04 includes a casing I06 having abore in which a valve plunger I08 is mounted, the plunger being normallyheld in theposition shown by a spring I I0. The tension of spring IIOmay be adjusted by a nut I I2 engaging threads in casing I06 to controlthe pressure in chamber 68 at which the starting device operates.

Casing I06 has an inlet port I I4 connected to a source of 'gas underpressure, and an outlet port II6 connected by a conduit II8 to channel94. Another outlet port I spaced from port H6 is connected by a conduitI22 to passage I02. In the normal position of plunger I08 a groove I24in the plunger connects ports II 4 and H6 and another groove I26establishes fluid connection from port I20 to a chamber I21 at the endof casing I06. When plunger I08 is shifted with to the other end of thestroke, as limited by a threaded ring I28, groove I24 connects inletport II4 with port I20, and another groove I80 connects port 6 to a ventport I82.

For moving plunger I08, the end of casing I06 has a nut I88 with athrough passage I84.

Nut I88 clamps a bushing I86, the end of which forms a valve seatengaged by the end of plunger I08. Passage I84 is connected by a branchconduit I86 to conduit I88 which connects with inlet port II4. Branchconduit I86 has an adjustable throttle valve I40 which can provide arestriction greater than any restriction from conduit I88 to chamber 68.When the desired pressure is developed in chamber 68, the pressure inpassage I84 acting on the end of plunger I08 moves the plunger againstthe action of spring IIO to connect port I20 to inlet port I I4 forprocuring opening of valve 66 for starting the unit.

A small bleed passage .I40 in casing I06 provides fluid connection fromthe end of plunger I08 to groove I80 which connects with vent port I82.This permits gas. leaking past the end of plunger I08 to be vented sothat the plunger will not be moved from the position shown until thedesired pressure has been built up in chamber 68.

A passage I44 in casing 86 connects passage 88 with groovev I08 in cap82 and is closed by a checie valve I46. After the starting unit has015-- erated and conduit I22 is vented by plunger I08 returning to theposition shown, gas at the right of piston 16 in cylinder 14 may escapepast valve I46 so that piston 16 may move into a position for closingpoppet valve 66.

The piston assemblies may be automatically moved to the outer ends oftheir stroke before the starting devices operate. :The structure is thesame for each piston assembly and only one of the structures will bedescribed. Compressor piston I8 has projecting concentric sleeves I48and I48, Fig. 4, connected at their outer ends to form a plunger I50sliding in an annular space "ISI between a sleeve I52 and a smallersleeve I58 mounted within the unit. Only one plunger is shown, but; forpurposes of balance, two oppositely placed plungers may be advantageous.

Gas under pressure is admitted by a supply valve I58 to the left handend of space I5| to move the piston assembly of which piston I8 is apart. The supply valve casing I54 has a sliding plunger valve I56 heldin the position shown by a spring I58. In this position gas entering aninlet port I60 passes around a groove I62 in valve I56 to an outlet portI64 connected by a conduit I66 to the end of a bore I68 in-a casing I10at the end of sleeve I52. From bore I68 gas under pressure passesthrough a channel I12 in casing I10 and a channel I14 in head I15 onsleeves I52 and I58 to the inner end of space I5I. Gas entering the endof this cylinder moves plunger I50 to the right, carrying with it theattached piston assemblyand moving the piston assembly into startingposition.

As plunger I50 moves tothe right, it uncovers a port I16 connected by aconduit I18 to a passage I80 in a cap I8I in the end of casing I54.

7 Gas entering this passage acts on the end of 76 release valve.

After the engine is started, plunger I50 acts as a pump forcing gasunder pressure through passage I'I4 past a disc valve I94 and through achannel I96 to a conduit I98 leading to the left hand end of easing I54.Pressure entering the casing acts on the end of valve plunger I56 toreturn it to the position shown. While gas under pressure is beingadmitted to the balance pump.

valve I90 is moved into a position to close passage I96. This passageis'opened upon return of valve I90 tothe normal position shown.

The starting system above described is claimed in the copendingapplication of Cooper, Serial No. 550,875, now Patent No. 2,439,453 ofApril 13, 1948. The present invention relates to the arrangementby.which any one of the number of units in the power plant may bestarted selectively by a starting system of this character:

Referring to Fig. 4, the supply of starting gas may be controlled by avalve 200. may include a casing 202 having a slide valve 204 moved in a,direction to cut oil fluid, connection between an inlet port 206 and anoutlet port 208 by a spring 2I0. Port 208 is connected by a conduit 2I2to the port I60 oi the supply valve. The plunger 204 is moved in adirection to provide fluid connection through the valve by a solenoid2I4. Port 206 is connected to a main conduit 2I6 leading to a supply ofgas under pressure which may be, for example, a tank of compressed airor gas, or a cartridge discharging device. Conduit 2I6 has a manuallycontrolled valve 2I8 which is located at the control station for thepower plant.

As shown in Fig. 5 there is a control valve 200 for each of the severalgenerators in the power plant and each control valve'is adapted to admitthe compressed gas to the above described starting system for thegenerator with which the control valve is associated. An electricalselector 220 located at thecontrol station and having a manually movableindicator 222 adapted to complete a circuit through a source of powerrepresented by a battery 224 and any one of the control valves 200selectively dependent upon the location of the indicator 222. As shown,contacts 226 engageableby the indicator 222 are connected to thesolenoids oi the control valves and the other terminal of each of thesolenoids is grounded at 228. The indicator 222 is connected through thesource of power to a around 220 to complete the circuit through theindividual control valves.

In starting the power plant, the operator. by adjustment of theindicator 222, selects which of the units he wishes to start and bycompleting the circuit through'the solenoid or the selective controlvalve establishes fluid connection from conduit M6 to the supply valveoi the selective unit. By opening valve *2I8 the starting system ior theselected unit is then set in operation and continues to operate untilthe selected unit Is running. This procedure is repeated ior each of theunits until all of the units are running. If any unit stalls, thearrangement described permits the operator to set in operation thestarting system for the stalled unit without afiecting the remainingunits. The use of an electrical selector system permits the eliminationof all pneumatic or fluid circuits from the control station to the powerplant, the only line necessary being the main supply conduit 2l6.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaims.

I claim:

1. A control system including a number of free piston units and astarting mechanism for each unit, including a pressure operated startingdevice and an automatic supply valve for said device, said system alsoincluding a conduit having a supply of starting gas, a branch conduitfrom said supply conduit to each supply valve and a normally. closedcontrol valve in each branch conduit, in combination with a selectorThis 'valve including a manually movable indicator for selecting whichunit is to be started, and an electrical circuit for each control valve,said indicator having associated therewith contact means for completingany of the electrical circuits selectively and electrical meansassociated with each control valve for operating said valve when theassociated circuit is completed.

2. A control system including a number of iree piston units and astarting mechanism for each unit, including a pressure operated startingdevice and an automatic supply valve for said device, said system alsoincluding a conduit having a supply of starting gas, a branch conduitfrom said supply conduit to each supply valve and a normally closedcontrol valve in each branch conduit, in combination with a singleelectrical control means including a number of parallel electricalcircuits with one circuit for each'control valve, electrically actuatedmeans associated with each control valve and included in the associatedcircuit for actuating said valve, and a selector switch for completingeach of said circuits selectively, said switch being manually actuatedfor the purpose of selecting which of the free piston units is to bestarted.

DONALD E. MEIIZLER.

REFERENCES CITED The following references are of record in the die ofthis patent:

UNITED STATES PATENTS Number Name Date 2,215,326 Janicke Sept. 17, 19402,260,252. John et al. Oct. 21, 1941 2,306,978 Pescara Dec. 29, 19422,344,058 Pescara Mar. 4, 1944 2,423,720 Mullejans et al. July 8, 19472,434,778 Welsh Jan. 20, 1948 2,469,739 Meitzler May 10, 1949 FOREIGNPATENTS Number Country Date Great Britain Dec. 11, 1941

